Hydrogen sulphide and mercaptans scavenging compositions

ABSTRACT

The present invention relates to a composition for scavenging hydrogen sulphide and/or mercaptans in hydrocarbon streams, the composition comprising an oxazolidine compound and a synergistic additive.

TECHNICAL FIELD

The present invention pertains to a novel hydrogen sulphide and mercaptans scavenging composition comprising an oxazolidine compound and an additive. The present invention also pertains to the use of the additive to improve the efficiency of an oxazolidine compound for scavenging hydrogen sulphide and mercaptans in hydrocarbon streams. The present invention also relates to a method for scavenging hydrogen sulphide and/or mercaptans comprising contacting a hydrocarbon stream such as crude oil, fuel or natural gas with the scavenging composition of the invention.

BACKGROUND OF THE INVENTION

Hydrogen sulphide is a colourless and fairly toxic, flammable and corrosive gas which also has a characteristic odour at a very low concentration. Hydrogen sulphide dissolves in hydrocarbon and water streams and is also found in the vapour phase above these streams and in natural gas. The hydrogen sulphide emissions can therefore be a nuisance to workers operating in the drilling, production, transport, storage, and processing of crude oil and in the storage of fuel. Hydrogen sulphide may also react with hydrocarbon components present in fuel. It would therefore be desirable for the workers' comfort and safety to reduce or even eliminate the hydrogen sulphide emissions during the manipulation of said products.

Legislation has been in place for years, imposing strict regulations on hydrogen sulphide levels of hydrocarbon streams pipelines, and in storage and shipping containers. A variety of chemical scavengers are available to reduce both the concentration and corresponding hazard of hydrogen sulphide in produced gas, crude oil and refined products. Some of the most common methods for treating hydrogen sulphide include triazine, glyoxal, as well as metal-based scavengers. Glyoxal has been used extensively as hydrogen sulphide scavenger but suffers from a major drawback since aqueous glyoxal solutions are highly corrosive and cannot be used for a gas tower application. Triazines have recently become a more common chemical scavenger used for treating hydrogen sulphide from hydrocarbon streams. However, many drawbacks are reported that are linked to the use of triazines.

Others hydrogen sulphide scavengers have been developed, and among them scavengers based on oxazolidine, like 3,3′-methylenebis(5-methyloxazolidine), known as MBO. A method for scavenging hydrogen sulphide from sour hydrocarbon substrates has been described in WO 98/02501. MBO presents the advantage to be less toxic and to create no scales in the conditions where triazine does.

However, this technology requires an important contact time in order to be efficient in sulphur removal and thus involves injection of higher doses.

Formulations of MBO with promoters, also named boosters, have been developed to enhance the efficiency of MBO. For example, WO 2017/102693 describes a composition comprising MBO and one or more additive selected among urea, urea derivatives, amino acids, guanidine, guanidine derivatives or 1,2-diols, said composition being used in the removal of sulphur compounds from process streams.

It would be useful to provide a composition enhancing the H₂S scavenging properties of MBO.

SUMMARY OF THE INVENTION

The present invention relates to a composition for scavenging hydrogen sulphide and mercaptans in hydrocarbon streams, said composition comprising an oxazolidine compound and an additive, said additive being a modified alkylphenol-aldehyde resin obtainable by a Mannich reaction of an alkylphenol-aldehyde condensation resin,

-   -   with at least one aldehyde and/or one ketone having 1 to 8         carbon atoms; and     -   at least one hydrocarbon compound having at least one         alkylmonoamine or alkylpolyamine group having from 2 to 30         carbon atoms, preferably from 4 to 30 carbon atoms,     -   and optionally with alkylene oxide comprising from 2 to 6 carbon         atoms, preferably from 2 to 4 carbon atoms, in order to provide         from 2 to 60 alkylene oxide groups per resin;

said alkylphenol-aldehyde condensation resin being obtainable by condensation;

-   -   of at least one alkylphenol substituted by at least one linear         or branched alkyl group having 1 to 30 carbon atoms; and     -   at least one aldehyde and/or one ketone having 1 to 8 carbon         atoms.

According to a particular embodiment, the alkylphenol substituted by at least one linear or branched alkyl group having 1 to 30 carbon atoms is substituted in para position, preferably is p-nonylphenol.

According to a particular embodiment, the aldehyde and/or a ketone is chosen from formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, 2-ethyl hexanal, benzaldehyde, or acetone.

According to a particular embodiment, the hydrocarbon compound having at least one alkylmonoamine or alkylpolyamine group having from 4 to 30 carbon atoms is selected from alkylamines having at least one primary amine group, preferably from hydrocarbon compounds compound, all the amine groups of which are primary amines.

According to a particular embodiment, the modified alkylphenol-aldehyde resin is obtainable from p-nonylphenol, formaldehyde and at least one hydrocarbon compound having at least one alkylmonoamine or alkylpolyamine group having from 4 to 30 carbon atoms having at least one primary amine group.

According to a particular embodiment, the oxazolidine compound is a selected from bisoxazolidines.

According to a particular embodiment, the composition comprises from 19 to 99% wt of oxazolidine compound(s) and from 1 to 50% wt of said additive(s), based on the total weight of the composition.

According to a particular embodiment, the weight ratio of oxazolidine compound(s) to said additive(s) ranges from 1 to 50, preferably from 2 to 30, preferably from 4 to 20.

According to a particular embodiment, the composition further comprises a solvent, preferably in an amount ranging from 1 to 80% wt, based on the total weight of the composition.

According to a particular embodiment, the composition comprises:

-   -   From 19 to 80% wt of oxazolidine compound(s),     -   From 1 to 30% wt of said additive(s), and     -   From 1 to 80% wt of solvent(s),     -   based on the total weight of the composition.

The present invention also relates to a use of the additive for improving the efficiency of an oxazolidine compound for scavenging hydrogen sulphide and/or mercaptans in hydrocarbon streams.

The present invention also relates to a hydrocarbon stream comprising hydrocarbons and a composition according to the invention.

According to a particular embodiment, the hydrocarbons are selected from crude oil, fuel oil, fuel, Light Petroleum Gas and natural gas.

The present invention also relates to a method for scavenging hydrogen sulphide and/or mercaptan in a hydrocarbon stream, comprising contacting the hydrocarbon stream with the composition according to the invention.

According to a particular embodiment of the method, the weight ratio between hydrogen sulphide contained in the hydrocarbon stream before the step of contacting and the composition ranges from 1:2 to 1:0.05, preferably from 1:1 to 1:0.1, more preferably from 1:0.9 to 1:0.2, even more preferably from 1:0.7 to 1:0.3 and advantageously from 1:0.8 to 1:0.4.

The composition of the present invention enables to reduce the treat rate, i.e. reduce the amount of MBO necessary to scavenge a given amount of hydrogen sulphide from the sulphur containing stream.

DETAILED DESCRIPTION OF THE INVENTION

The present invention concerns a hydrogen sulphide and mercaptans scavenging composition comprising at least one oxazolidine compound and at least one additive.

According to the invention, the additive is an alkylphenol-aldehyde resin that is modified by an alkylmonoamine or an alkylpolyamine group and that is optionally alkoxylated, preferably that is optionally ethoxylated.

According to an embodiment of the present invention, the additive is a modified alkylphenol-aldehyde resin obtainable by a Mannich reaction of an alkylphenol-aldehyde condensation resin,

-   -   with at least one aldehyde and/or one ketone having 1 to 8         carbon atoms; and     -   at least one hydrocarbon compound having at least one         alkylmonoamine or alkylpolyamine group having from 4 to 30         carbon atoms;

said alkylphenol-aldehyde condensation resin being itself obtainable by condensation;

-   -   of at least one alkylphenol substituted by at least one linear         or branched alkyl group having 1 to 30 carbon atoms; and     -   at least one aldehyde and/or one ketone having 1 to 8 carbon         atoms.

According to a particular embodiment, the oxazolidine compound is selected from bisoxazolidines, i.e. compounds comprising two oxazolidine cycles.

According to a particular embodiment, the oxazolidine compound replies to formula (I):

wherein

n is an integer ranging from 1 to 6, preferably from 1 to 2;

R1 and R2, identical or different, are selected from a hydrogen atom and a linear, branched or cyclic alkyl or alkenyl groups having from 1 to 6 carbon atoms, preferably from 1 to 2 carbon atoms.

Preferably, the oxazolidine compound is 3,3′-methylenebis(5-methyloxazolidine).

According to the invention, the “additive” used in combination with the oxazolidine compound is also referred to by the expression the “synergistic additive”.

The additive or synergistic additive of the invention is a modified alkylphenol-aldehyde resin obtainable by a Mannich reaction of an alkylphenol-aldehyde condensation resin,

-   -   with at least one aldehyde and/or one ketone having 1 to 8         carbon atoms, preferably 1 to 4 carbon atoms; and     -   at least one hydrocarbon compound having at least one         alkylmonoamine or alkylpolyamine (alkylamine) group having from         2 to 30 carbon atoms, preferably from 4 to 30 carbon atoms,     -   and optionally with at least one alkylene oxide, preferably         comprising from 2 to 6 carbon atoms, more preferably from 2 to 4         carbon atoms;

said alkylphenol-aldehyde condensation resin being itself obtainable by condensation;

-   -   of at least one alkylphenol substituted by at least one linear         or branched alkyl group having 1 to 30 carbon atoms, preferably         a monoalkylphenol; and     -   at least one aldehyde and/or one ketone having 1 to 8 carbon         atoms, preferably 1 to 4 carbon atoms.

The alkylphenol-aldehyde resins are known per se. According to a preferred embodiment, the modified alkylphenol-aldehyde resins used in the invention can be obtained from at least one alkylphenol substituted in para position; preferably at least nonylphenol. The average number of phenolic nuclei per molecule of preferred nonylphenol-aldehyde resin is preferably superior to 6 and inferior or equal to 25, more preferably comprised within the range 8 to 17, and advantageously within the range 9 to 16 phenolic nuclei per molecule. The average number of phenolic nuclei per molecule can be determined by RMN or GPC.

According to a preferred embodiment, the modified alkylphenol-aldehyde resins used in the invention can be obtained from at least one aldehyde and/or one ketone chosen from formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, 2-ethyl hexanal, benzaldehyde, acetone, preferably at least formaldehyde. According to a preferred embodiment, the modified alkylphenol-aldehyde resins used in the invention can be obtained from at least one alkylamine having at least one primary amine group, and advantageously at least one compound, all the amine groups of which are primary amines. According to a preferred embodiment, the modified alkylphenol-aldehyde resins used in the invention can be obtained from at least one alkylamine with an aliphatic chain having between 12 and 24 carbon atoms, preferably between 12 and 22 carbon atoms. Such modified alkylphenol-aldehyde resins can be prepared according to the protocol described in patent applications WO 2012/085865 (A1) and WO 2016/162392 (A1).

According to a particularly preferred embodiment, the modified alkylphenol-aldehyde resins used in the invention can be obtained from at least one alkylamine having at least one primary amine group and comprising an aliphatic chain having between 12 and 24 carbon atoms, preferably between 12 and 20 carbon atoms.

The commercially-available alkylamines are in general not pure compounds but mixtures. Among the commercially-available alkylamines which are suitable, there can in particular be mentioned the following alkylamines with an aliphatic chain marketed under the names: Noram®, Duomeen®, Dinoram®, Trinoram®, Triameen®, Armeen®, Polyram®, Lilamin® and Cemulcat®. The viscosity of the modified alkylphenol-aldehyde condensation resins used in the invention diluted with 30% by mass of aromatic solvent measured at 50° C. using a dynamic rheometer with a shear rate of 100 s⁻¹ is in general ranging from 1,000 to 10,000 mPa·s, preferably from 1,500 to 6,000 mPa·s, and advantageously from 2,500 to 5,000 mPa·s.

According to a particular preferred embodiment, the modified alkylphenol-aldehyde resins used in the invention is an alkoxylated modified alkylphenol-aldehyde resins that can be obtained from at least one alkylene oxide comprising from 2 to 6 carbon atoms, preferably from 2 to 4 carbon atoms and from at least one alkylamine comprising from 2 to 12 carbon atoms and one or three primary amine groups, preferably two primary amine groups. According to an embodiment, the modified alkylphenol-aldehyde resins used in the invention is an ethoxylated alkylphenol-aldehyde resin modified by ethylene diamine.

According to an embodiment, the H₂S and mercaptans scavenging composition comprises from 19 to 99% wt, preferably from 40 to 98% wt, more preferably from 55 to 79%, more preferably from 60 to 95% wt, even more preferably from 70 to 90% wt of oxazolidine compound(s) and from 0.5 to 50% wt, preferably from 1 to 45% wt, even more preferably from 1.5 to 40% wt, more preferably from 2 to 30% wt of synergistic additive(s), based on the total weight of the H₂S and mercaptans scavenging composition. Preferably, the weight ratio oxazolidine compound(s) to synergistic additive(s) ranges from 1 to 100, preferably from 1 to 50, more preferably from 2 to 30, even more preferably from 4 to 20.

According to an embodiment, the H₂S and mercaptans scavenging composition further comprises at least one solvent.

Preferably, the solvent is selected from poly alkyl ethers, aliphatic or aromatic solvents, more preferably from aromatic solvents, such as N-methylpyrrolidone, butyl carbitol, xylene, toluene, and benzene. It has been observed that the scavenging efficiency of the compositions of the invention is not dependent on the solvent. However, depending on the final use of the scavenging composition, a solvent having a dual solubility, i.e. a water solubility and a solubility in hydrocarbons, can be preferred. Butyl carbitol is a suitable solvent since it has this dual solubility.

According to this embodiment, the solvent represents from 1 to 80% wt of the composition, preferably from 5 to 70% wt, more preferably from 10 to 60% wt, even more preferably from 20 to 50% wt of the composition.

According to a particular embodiment of the invention, the composition comprises:

-   -   From 10 to 98% wt, preferably from 30 to 80% wt, more preferably         from 40 to 60% wt of oxazolidine compound(s),     -   From 0.5 to 30% wt, preferably from 1 to 20% wt, more preferably         from 2 to 15% wt, even more preferably from 3 to 10% wt of the         additive(s) defined in the invention, and     -   From 1.5 to 80% wt, preferably from 5 to 65% wt, more preferably         from 15 to 55% wt of solvent(s),     -   based on the total weight of the composition.

According to a particular embodiment of the invention, the composition comprises:

-   -   From 19 to 80% wt, preferably from 30 to 70% wt, more preferably         from 40 to 60% wt of oxazolidine compound(s),     -   From 1 to 30% wt, preferably from 1.5 to 20% wt, more preferably         from 2 to 10% wt of the additive(s) defined in the present         invention, and     -   From 1 to 80% wt, preferably from 15 to 65% wt, more preferably         from 25 to 55% wt of solvent(s),     -   based on the total weight of the composition.

According to an embodiment of the invention, the composition comprises:

-   -   From 19 to 80% wt, preferably from 30 to 70% wt, more preferably         from 40 to 60% wt of a bisoxazolidine,     -   From 1 to 30% wt, preferably from 1.5 to 20% wt, more preferably         from 2 to 10% wt of additive(s) selected from modified         alkylphenol-aldehyde resin, and     -   From 1 to 80% wt, preferably from 15 to 65% wt, more preferably         from 25 to 55% wt of solvent(s),     -   based on the total weight of the composition.

According to an embodiment of the invention, the composition comprises:

-   -   From 10 to 98% wt, preferably from 30 to 80% wt, more preferably         from 40 to 60% wt of bisoxazolidine compound(s),     -   From 0.5 to 30% wt, preferably from 1 to 20% wt, more preferably         from 2 to 15% wt, even more preferably from 3 to 10% wt of the         additive(s) defined in the invention, and     -   From 1.5 to 80% wt, preferably from 5 to 65% wt, more preferably         from 15 to 55% wt of solvent(s),     -   based on the total weight of the composition,

wherein the additive(s) are selected from (i) nonylphenol-aldehyde resin modified by formaldehyde and alkylamine(s) having at least one primary amine group and comprising an aliphatic chain having between 12 and 24 carbon atoms, (ii) nonylphenol-aldehyde resin modified by formaldehyde, ethylene diamine and ethylene oxide.

The present invention also concerns the use of the synergistic additive defined above for improving the efficiency of the oxazolidine compound defined above for scavenging hydrogen sulphide (H2S) and/or mercaptans in hydrocarbon streams.

By hydrocarbon stream is meant either a single-phase hydrocarbon stream or a multiphase system comprising oil/water or oil/water/gas or gas/water.

Preferably, the weight ratio oxazolidine compound(s) to synergistic additive(s) ranges from 1 to 50, preferably from 2 to 30, preferably from 4 to 20.

Hydrocarbon streams contain H₂S and/or mercaptans, in an amount for example ranging from 1 to 10 000 ppm. Mercaptans that can be removed from hydrocarbon streams within the framework of the present invention may be C₁-C₆ mercaptans, such as C₁-C₄ mercaptans.

The present invention also concerns the use of the composition defined above as a H₂S and/or mercaptans scavenger in hydrocarbon streams, said hydrocarbon streams being preferably selected from crude oil, fuel and natural gas. The composition of the invention is contacted with hydrocarbon streams such as crude oil, fuel or natural gas in order to reduce the amount of hydrogen sulphide (H₂S) and mercaptans. Hydrocarbon streams may be selected from crude oils and fuels which typically comprise more than 60% wt of paraffins, preferably more than 70% wt of paraffins and even more preferably more than 75% wt of paraffins, based on the total weight of the crude oils and fuels. Hence, hydrocarbon streams may be selected from crude oils and fuels which typically comprise less than 30% wt of aromatics, preferably less than 10% wt of aromatics and even more preferably less than 5% wt of aromatics, based on the total weight of the crude oils and fuels.

Hydrocarbon streams contain H₂S and/or mercaptans, in an amount for example ranging from 1 to 10 000 ppm. Mercaptans that can be removed from hydrocarbon streams within the framework of the present invention may be C₁-C₆ mercaptans, such as C₁-C₄ mercaptans.

According to an embodiment of the present invention, the weight ratio H₂S:scavenging composition ranges from 1:2 to 1:0.05, preferably from 1:1 to 1:0.1, more preferably from 1:0.9 to 1:0.2, even more preferably from 1:0.7 to 1:0.3 and advantageously from 1:0.8 to 1:0.4. In this ratio, H₂S represents the amount of hydrogen sulphide in the hydrocarbon streams, before contacting with the scavenging composition of the invention.

The present invention also concerns hydrocarbon streams comprising hydrocarbons and the composition of the invention. The hydrocarbon streams considered in the present invention may be either single-phase hydrocarbon streams or multiphase systems comprising oil/water or oil/water/gas or gas/water.

Hydrocarbons may be selected from crude oil, fuel oil, fuel, Light Petroleum Gas and natural gas. Hydrocarbon streams may be selected from crude oils and fuels which typically comprise more than 60% wt of paraffins, preferably more than 70% wt of paraffins and even more preferably more than 75% wt of paraffins, based on the total weight of the crude oils and fuels. Hence, hydrocarbon streams may be selected from crude oils and fuels which typically comprise less than 30% wt of aromatics, preferably less than 10% wt of aromatics and even more preferably less than 5% wt of aromatics, based on the total weight of the crude oils and fuels.

Hydrocarbon streams contain H₂S and/or mercaptans, in an amount for example ranging from 1 to 10 000 ppm. Mercaptans that can be removed from hydrocarbon streams within the framework of the present invention may be C₁-C₆ mercaptans, such as C₁-C₄ mercaptans.

The composition of the invention may represent from 0.0005 to 5% by weight of the total weight of the hydrocarbon streams.

According to an embodiment of the present invention, the weight ratio H₂S:scavenging composition ranges from 1:2 to 1:0.05, preferably from 1:1 to 1:0.1, more preferably from 1:0.9 to 1:0.2, even more preferably from 1:0.7 to 1:0.3 and advantageously from 1:0.8 to 1:0.4. In this ratio, H₂S represents the amount of hydrogen sulphide of the hydrocarbon streams, before contacting with the scavenging composition of the invention.

EXAMPLES

The invention is now described with the help of the following examples, which are not intended to limit the scope of the present invention, but are incorporated to illustrate advantages of the present invention and best mode to perform it. The following examples also demonstrated the effectiveness of scavenging compositions of the present invention, which can be a composition comprising of MBO (3,3′-methylenebis(5-methyloxazolidine) and modified alkylphenol-aldehyde resin that is optionally ethoxylated.

Example 1: Protocol of Experiment for the Measurement of H₂S Scavenging Ability of the Scavenging Compositions Under Modified ASTM D-5705 Conditions

ASTM D-5705 is recommended for measurement of Hydrogen sulfide in a vapor phase above the residual fuel oils. Performance evaluation of the various products and formulations developed as Hydrogen Sulfide Scavengers were evaluated using modified ASTM D-5705 test method.

In a typical experiment, 1 liter tin metal bottles with inner and outer caps were used to prepare and hold the test media. Dearomatized hydrocarbon solvents (with high boiling range i.e. >120° C. and flash point above 65° C. with aromatic content less than 0.1%) is used for the tests.

In a representative experimental set, a defined amount of H₂S saturated hydrocarbon solvent, typically between 2000 and 7000 ppm by weight of H₂S, was inserted in a well-sealed plastic drum containing 10 liters of dearomatized hydrocarbon solvent. The plastic drum was then kept on a reciprocating shaking machine for 5 min to allow proper mixing of the H₂S gas. 500 mL of the H₂S containing dearomatized hydrocarbon solvent were then transferred to first tin metal bottle and sealed with inner and outer caps. The tin metal bottle was then kept in a water bath at 60° C. for two hours. After two hours, the tin metal bottle was taken out and cooled down to room temperature under running tap water and kept aside. An H₂S detecting tube (Drager tube, with typical detection limit ranging from 100 to 70 000 ppm by weight) was inserted in a rubber cork through a hole having the same diameter as the detecting tube. The sealed ends of the H₂S detecting tube were opened with an appropriate opener, one end of the tube being attached to Drager pump. The inner and outer caps of the tin metal bottles were opened and very quickly the rubber cork with H₂S detector tube was inserted inside the opening of the tin metal bottle. The H₂S gas in the vapor phase of the tin metal bottle was then pulled through the H₂S measuring tube using Dräger pump attached at the other end of the tube. The detector tube was removed after complete decompression of the pump. H₂S concentration was read from the tubes calibration scale (typically color change from colorless to brown). This reading was noted as a reference Blank reading of H₂S amount.

Further, remaining H₂S containing dearomatized hydrocarbon solvent was transferred into other tin metal bottles, each with 500 mL of the dearomatized hydrocarbon, all bottles being pre-charged with the H₂S scavengers at different ratios of scavenger against H₂S, based on the Blank reading. Typical H₂S:scavenger ratios employed were 1:1, 1:0.8, 1:0.6, 1:0.4, 1:0.2 and 1:0.1. All the metal bottles were kept in a water bath for two hours at 60° C. Similar protocol was employed to measure the H₂S in the vapor phase of all the bottles as used to make the Blank reading. The difference between the Blank H₂S concentration and H₂S concentration observed with different concentrations of the scavenging products and formulations are noted as % scavenging. A higher % Scavenging with lower concentration of the scavenging product is considered as better H₂S scavenger for the set of experiment.

The protocol of measurement was repeated three times with each scavenging composition and the indicated percentage was calculated based on the average of the measurements.

Example 2: Measurement of H₂S Scavenging Ability of the Scavenging Compositions of the Invention Under Modified ASTM D-5705 Conditions, as Detailed in Example 1

Table 1 below summarizes the scavenging compositions that were tested. The synergistic additive used in Examples I1, I2 and I3 according to the invention was a nonylphenol-formaldehyde resin modified by reaction with formaldehyde and tallow propylene triamine having typically a Mw of 5000 Daltons. This product is commercialized in the form of a solution with an active content of about 45 to 55% w/w, i.e. comprising 45-55 wt % additive and 45-55 wt % solvent. The concentration of additive reported in Table 1 corresponds to the actual amount of active ingredient in the scavenging composition. As such, composition I1 comprises 10 wt % of additive solution at 45-55 wt % of active content, which correspond to 4.5-5.5 wt % of active ingredient in the scavenging composition.

TABLE 1 scavenging compositions (in wt % based on the total weight of the composition) Synergistic additive H₂S (wt % of active ingredient) Solvent scavenging MBO (modified nonylphenol- (wt %) composition (wt %) formaldehyde resin) xylene C1 (comparative) 50 0 50 C2 (comparative) 100 0 0 I1 50 4.5-5.5 44.5-45.5 I2 50 2.25-2.75 47.25-47.75 I3 45 2.25-2.72 52.25-52.75

Table 2 below shows the percentage of H₂S reduction based on the measured H₂S amount in vapour phase after treatment with comparative MBO compositions (C1 and C2) and H₂S scavenging compositions of the invention (I1, I2 and I3).

TABLE 2 Scavenging efficiency (% of H₂S reduction) of the scavenging compositions H₂S scavenging Sample1 Sample2 Sample3 Sample4 Sample5 Sample6 Sample7 composition (blank) [1:0.1] [1:0.2] [1:0.4] [1:0.6] [1:0.8] [1:1] C1 (50% MBO) 0 3 12 43 74 92 100 C2 (100% MBO) 0 15 45 93 100 100 100 I1 (50% MBO; 0 12 35 92 100 100 100 4.5-5.5% additive) I2 (50% MBO; 0 12 40 65 95 100 100 2.25-2.785% additive) I3 (45% MBO; 0 9 35 76 98 100 100 2.25-2.75% addtive)

The results in Table 2 clearly show that the scavenging compositions of the present invention are much more efficient than the scavenging compositions of the prior art.

If we refer for example to sample 4 wherein the weight ratio H₂S:scavenging composition is 1:0.4, we can observe that more than 92% of the H₂S have been scavenged with the scavenging composition I1 according to the invention whereas only 43% of the H₂S have been scavenged with the scavenging composition C1 of prior art, although both compositions comprise 50% MBO.

Example 3: Measurement of H₂S Scavenging Ability of the Synergistic Additive Under Modified ASTM D-5705 Conditions, as Detailed in Example 1

The synergistic additive of the invention was also tested alone for its ability to scavenge hydrogen sulphide using the modified ASTM D-5705 method. The aim was to determine the contribution of the synergistic additive to the total scavenging ability of the composition.

The protocol of measurement was repeated three times with each composition of synergistic additive and the indicated percentage was calculated based on the average of the measurements.

Table 3 below shows the percentage of H₂S reduction based on the measured H₂S amount in vapour phase after treatment with the additive in a solvent. The tested comparative composition C3 comprises 5% by weight of active ingredient of the same modified nonylphenol-formaldehyde resin as in Example 2 and 95% by weight of xylene. Similarly C4 comprise 10% by weight of the same modified nonylphenol-formaldehyde resin and 90% by weight of xylene.

TABLE 3 % Scavenging efficiency (% of H₂S reduction) of the synergistic additive synergistic additive Sample1 Sample2 Sample3 Sample4 Sample5 Sample6 Sample7 composition (blank) [1:0.1] [1:0.2] [1:0.4] [1:0.6] [1:0.8] [1:1] C3 (5% additive) 0 0 0 0 0 0 0 C4 (10% additive) 0 0 0 0 0 0 0

The results in Table 3 clearly show that the synergistic additive has no direct effect on the scavenging of hydrogen sulphide. This confirms that said additive cannot itself scavenge H₂S but has a boosting effect when used together with an H₂S scavenging compound.

Example 4: Measurement of H₂S Scavenging Ability of the Scavenging Compositions of the Invention Under Modified ASTM D-5705 Conditions

The following protocol has been followed:

ASTM D-5705 is recommended for measurement of Hydrogen sulfide in a vapor phase above the residual fuel oils. Performance evaluation of the various products and formulations developed as Hydrogen Sulfide Scavengers were evaluated using modified ASTM D-5705 test method.

In a typical experiment, 1 liter tin metal bottles with silicon septa were used to prepare and hold in the two test media:

-   -   Test media 1: a dearomatized hydrocarbon solvent having an         initial boiling point higher than 120° C., a final boiling point         lower than 250° C. (the difference between the final boiling         point and the initial boiling point ranges from 20 to 35° C.)         and a flash point above 65° C. with aromatic content less than         0.1% wt and a paraffin content of more than 75% wt,     -   Test media 2: a dearomatized hydrocarbon solvent having an         initial boiling point higher than 120° C., a final boiling point         higher than 250° C. (the difference between the final boiling         point and the initial boiling point ranges from 40 to 50° C.)         and a flash point above 100° C. with aromatic content less than         0.05% wt and a paraffin content of more than 75% wt.

In a representative experimental set, a defined amount of H₂S saturated hydrocarbon solvent, typically between 2000 and 7000 ppm by weight of H₂S, was injected in 1 liter tin metal bottle pre-filled with 500 ml of dearomatized hydrocarbon solvent through the silicon septa fixed at the opening of the bottle using micro-syringe. The metal bottle was then kept on a reciprocating shaking machine for 5 min to allow proper mixing of the H₂S gas. The tin metal bottle was then kept in a water bath at 60° C. for two hours. After two hours, the tin metal bottle was taken out and cooled down to room temperature under running tap water and kept aside. An H₂S detecting tube (Drager tube, with typical detection limit ranging from 100 to 70 000 ppm by weight) was inserted in a rubber cork through a hole having the same diameter as the detecting tube. The sealed ends of the H₂S detecting tube were opened with an appropriate opener, one end of the tube being attached to Drager pump. The silicon septa mounted at the opening of the tin metal bottles was removed and very quickly the rubber cork with H₂S detector tube was inserted inside the opening of the tin metal bottle. The H₂S gas in the vapor phase of the tin metal bottle was then pulled through the H₂S measuring tube using Drager pump attached at the other end of the tube. The detector tube was removed after complete decompression of the pump. H₂S concentration was read from the tubes calibration scale (typically color change from colorless to brown). This reading was noted as a reference Blank reading of H₂S amount.

Further, same amount of H₂S containing dearomatized hydrocarbon solvent was injected into other tin metal bottles, which are pre-filled with 500 mL of the dearomatized hydrocarbon, and H₂S scavengers at different ratios of scavenger against H₂S, based on the Blank reading. Typical H₂S:scavenger ratios employed were 1:1, 1:0.8, 1:0.6, 1:0.4, 1:0.2 and 1:0.1. All the metal bottles were kept in a water bath for two hours at 60° C. Similar protocol was employed to measure the H₂S in the vapor phase of all the bottles as used to make the Blank reading. The difference between the Blank H₂S concentration and H₂S concentration observed with different concentrations of the scavenging products and formulations are noted as % scavenging. A higher % Scavenging with lower concentration of the scavenging product is considered as better H₂S scavenger for the set of experiment.

The protocol of measurement was repeated three times with each scavenging composition and the indicated percentage was calculated based on the average of the measurements.

Table 4 below summarizes the scavenging compositions that have been tested. The synergistic additive used in Examples I4, I5 and I6 is identical to the additive used in example 2, except that the solvent xylene has been replaced by the solvent butyl carbitol. The concentration of additive reported in Table 4 corresponds to the actual amount of active ingredient in the scavenging composition. As such, composition I4 comprises 5 wt % of additive solution at 45-55 wt % of active content, which correspond to 2.25-2.75 wt % of active ingredient in the scavenging composition.

TABLE 4 scavenging compositions (in wt % based on the total weight of the composition) Synergistic additive Solvent H₂S (wt % of active ingredient) (wt %) scavenging MBO (modified nonylphenol- Butyl composition (wt %) formaldehyde resin) carbitol C5 50 0 50 I4 50 2.25-2.75 47.25-47.75 I5 50 1.13-1.38 48.87-48.62 I6 50 0.45-0.55 49.55-49.45

Table 5 below shows the percentage of H₂S reduction based on the measured H₂S amount in vapour phase after treatment with a comparative MBO composition (C5) and H₂S scavenging compositions of the invention (I4, I5 and I6).

TABLE 5 Scavenging efficiency (% of H₂S reduction) of the scavenging compositions H₂S scavenging composition Sample1 Sample2 Sample3 Sample4 Sample5 Sample6 Sample7 in Test media (blank) [1:0.1] [1:0.2] [1:0.4] [1:0.6] [1:0.8] [1:1] C5 in Test Media 1 0 5 12 43 74 92 100 C5 in Test Media 2 0 10 26 78 85 100 100 I4 in Test Media 1 0 12 35 92 100 100 100 I4 in Test Media 2 0 18 46 98 100 100 100 I5 in Test Media 1 0 12 40 65 95 100 100 I6 in Test Media 1 0 10 40 64 88 100 100

The results in Table 5 clearly show that the scavenging compositions of the present invention are much more efficient than the scavenging compositions of the prior art, in both hydrocarbon streams that have been used as test media.

Example 5: Measurement of H₂S Scavenging Ability of the Scavenging Compositions of the Invention Under Modified ASTM D-5705 Conditions

Similar experiments as example 4 have been performed, except that another synergistic additive has been used and the solvent used is xylene. The synergistic additive used is a nonylphenol-aldehyde resin modified with ethylene diamine and ethoxylated groups with an amount of ethoxy groups ranging from 2 to 60, commercially available resin, comprising 70% wt of active matter and having a molecular weight of about 1200 to 4000 Da. The concentration of additive reported in Table 6 corresponds to the actual amount of active ingredient in the scavenging composition. As such, composition 17 comprises 5 wt % of additive composition at about 70 wt % of active content, which correspond to 3.5 wt % of active ingredient in the scavenging composition.

Table 6 below summarizes the scavenging compositions that have been tested.

TABLE 6 scavenging compositions (in wt % based on the total weight of the composition) H₂S Solvent scavenging MBO Synergistic additive (wt %) composition (wt %) (wt % of active ingredient) xylene C1 (comparative) 50 0 50 I7 50 3.5 41.5 I8 50 1.75 48.25 I9 50 0.7 49.3

Table 7 below shows the percentage of H₂S reduction based on the measured H₂S amount in vapour phase after treatment with comparative MBO composition (C1) and H₂S scavenging compositions of the invention (I7, I8 and I9).

TABLE 7 Scavenging efficiency (% of H₂S reduction) of the scavenging compositions H₂S scavenging composition Sample1 Sample2 Sample3 Sample4 Sample5 Sample6 Sample7 in Test media (blank) [1:0.1] [1:0.2] [1:0.4] [1:0.6] [1:0.8] [1:1] C1 in Test Media 1 0 5 12 43 74 92 100 C1 in Test Media 2 0 10 26 78 85 100 100 I7 in Test Media 1 0 32 48 88 98 100 100 I7 in Test Media 2 0 36 50 93 99 100 100 I8 in Test Media 1 0 30 40 83 93 100 100 I9 in Test Media 1 0 26 34 78 90 100 100

The results in Table 7 clearly show that the scavenging compositions of the present invention are much more efficient than the scavenging compositions of the prior art, in both hydrocarbon streams that have been used as test media.

Example 6: Measurement of H₂S Scavenging Ability of the Scavenging Compositions of the Invention in a Gaseous Hydrocarbon Stream

The experimental protocol is the following: a scavenging composition is introduced into a closed bottle. A gas mixture comprising nitrogen and 50 ppm by weight of H₂S is bubbled through the scavenging composition using a glass frit (0.2 LPM). The test is performed at 25° C. and ambient pressure. The H2S concentration in the gas phase (inside the bottle, above the scavenging composition) is lodged every 10 seconds for up to 80 min.

The breakthrough time is the time taken to give a gas phase H₂S concentration of 1 ppm.

The blank corresponds to the measurement performed in the presence of a solution free of MBO and free of synergistic additive(s). The synergistic additive is a nonylphenol-formaldehyde resin modified by reaction with formaldehyde and tallow propylene triamine having typically a Mw of 5000 Daltons (the same as used in example 2).

The scavenging compositions and the breakthrough time are detailed in table 8 below.

TABLE 8 blank C2 I10 I11 Xylene (% wt) — 0 5 2.5 MBO (% wt) — 100 90 95 Synergistic additive — 0 5 2.5 (% wt of active matter) Breakthrough time (min) 61.4 75.1 77.7 >80

As illustrated in table 8, the synergistic additive allows improving the scavenging performance of the compositions containing MBO. Indeed, scavenging compositions I10 and I11 according to the invention have a higher breakthrough time than composition C2 containing only MBO showing their better scavenging properties. 

1-15. (canceled)
 16. A composition for scavenging hydrogen sulphide and mercaptans in hydrocarbon streams, said composition comprising an oxazolidine compound and an additive, said additive being a modified alkylphenol-aldehyde resin obtainable by a Mannich reaction of an alkylphenol-aldehyde condensation resin, with at least one aldehyde and/or one ketone having 1 to 8 carbon atoms; and at least one hydrocarbon compound having at least one alkylmonoamine or alkylpolyamine group having from 2 to 30 carbon atoms, optionally with at least one alkylene oxide; said alkylphenol-aldehyde condensation resin being obtainable by condensation; of at least one alkylphenol substituted by at least one linear or branched alkyl group having 1 to 30 carbon atoms; and at least one aldehyde and/or one ketone having 1 to 8 carbon atoms.
 17. The composition according to claim 16, wherein the alkylphenol substituted by at least one linear or branched alkyl group having 1 to 30 carbon atoms is substituted in para position.
 18. The composition according to claim 16, wherein aldehyde and/or a ketone is chosen from formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, 2-ethyl hexanal, benzaldehyde, or acetone.
 19. The composition according to claim 16, wherein the hydrocarbon compound having at least one alkylmonoamine or alkylpolyamine group having from 2 to 30 carbon atoms is selected from alkylamines having at least one primary amine group.
 20. The composition according to claim 16, wherein the modified alkylphenol-aldehyde resin is obtainable from p-nonylphenol, formaldehyde and at least one hydrocarbon compound having at least one alkylmonoamine or alkylpolyamine group having from 2 to 30 carbon atoms having at least one primary amine group, and optionally with alkylene oxide selected from ethylene oxide and propylene oxide.
 21. The composition according to claim 16, wherein the oxazolidine compound is a selected from bisoxazolidines.
 22. The composition according to claim 16, wherein the composition comprises from 19 to 99% wt of oxazolidine compound(s) and from 1 to 50% wt of said additive(s), based on the total weight of the composition.
 23. The composition according to claim 16, wherein the weight ratio of oxazolidine compound(s) to said additive(s) ranges from 1 to
 100. 24. The composition according to claim 16, further comprising a solvent.
 25. The composition according to claim 16, comprising: From 19 to 80% wt of oxazolidine compound(s), From 1 to 30% wt of said additive(s), and From 1 to 80% wt of solvent(s), based on the total weight of the composition.
 26. Process for improving the efficiency of an oxazolidine compound for scavenging hydrogen sulphide and/or mercaptans in hydrocarbon streams, the process comprising a step of adding the additive defined in claim 16 in an oxazolidine compound.
 27. Hydrocarbon stream comprising hydrocarbons and a composition according to claim
 16. 28. Hydrocarbon streams according to claim 27, wherein the hydrocarbons are selected from crude oil, fuel oil, fuel, Light Petroleum Gas and natural gas.
 29. A method for scavenging hydrogen sulphide and/or mercaptan in a hydrocarbon stream, comprising contacting the hydrocarbon stream with the composition according to claim
 16. 30. The method according to claim 29, wherein the weight ratio between hydrogen sulphide contained in the hydrocarbon stream before the step of contacting and the composition ranges from 1:2 to 1:0.05.
 31. The composition according to claim 16, wherein the alkylphenol substituted by at least one linear or branched alkyl group having 1 to 30 carbon atoms is p-nonylphenol.
 32. The composition according to claim 16, wherein the hydrocarbon compound having at least one alkylmonoamine or alkylpolyamine group having from 2 to 30 carbon atoms is selected from hydrocarbon compounds compound, all the amine groups of which are primary amines.
 33. The composition according to claim 24, wherein the solvent is present in an amount ranging from 1 to 80% wt, based on the total weight of the composition. 